Kikuyu grass (Pennisetum clandestinum) is notoriously difficult to control — it spreads aggressively via stolons and rhizomes, and can quickly invade garden beds, smother ground covers, and strangle ornamentals. The good news is that with the right combination of methods, you can get on top of it without collateral damage to your other plants.
Why Kikuyu Is So Hard to Kill
Kikuyu is a warm-season grass originally from East Africa that thrives in New Zealand's temperate to subtropical climate, particularly in the upper North Island. Its underground rhizomes can extend deep into soil and regrow from tiny fragments, meaning a single missed piece can restart the invasion. Persistence is key — most control programmes require multiple treatments over one or more growing seasons.
Method 1: Selective Herbicides
Selective grass herbicides are the most effective chemical option for removing kikuyu from garden beds without harming broadleaf plants (shrubs, perennials, vegetables, and most groundcovers).
- Look for products containing fluazifop-p-butyl or haloxyfop as the active ingredient. These are graminicides — they target grasses only and leave broadleaf plants unharmed.
- Common NZ retail options include products such as Yates Grass Killer or similar fluazifop-based sprays, available at Bunnings or Mitre 10.
- Always read the label carefully. Some ornamental grasses, sedges, and grass-like plants (e.g. lomandra, carex, phormium) may be affected — check compatibility before spraying.
- Apply on a calm, dry day when rain isn't forecast for at least 24 hours. Kikuyu is best treated when it is actively growing (spring through summer).
- Expect to apply two or three rounds, spaced 4–6 weeks apart, as regrowth appears.
What About Glyphosate?
Glyphosate (e.g. Roundup) is a non-selective herbicide — it will kill kikuyu effectively, but it will also kill or damage any plant it contacts. It can be used carefully with a paintbrush or wick applicator to treat individual runners in tight spots, but it is not suitable for broadcast spraying near desirable plants.
Method 2: Manual Removal
For smaller infestations or areas where chemicals aren't suitable (e.g. near edible gardens or water features), manual removal is a viable — if labour-intensive — option.
- Use a garden fork or mattock to loosen the soil and trace out the rhizome network. Try to remove as much root material as possible.
- Do this in autumn or early spring when the soil is moist and roots are easier to extract.
- Bag and bin all removed material — do not compost kikuyu, as it can re-establish from fragments.
- Follow up regularly; even small pieces left behind will reshoot.
Method 3: Smothering and Solarisation
For larger areas you want to clear before replanting:
- Cardboard smothering (sheet mulching): Lay overlapping cardboard directly over the kikuyu, wet it thoroughly, then cover with 100–150 mm of bark mulch or compost. This blocks light and can suppress kikuyu over 3–6 months, though persistent rhizomes may still push through.
- Soil solarisation: In summer, cover the area with clear polythene sheeting and seal the edges. The heat build-up under the plastic can kill surface growth and shallow rhizomes over 6–8 weeks of hot weather. This works best in warmer NZ regions.
Method 4: Physical Barriers
Once you've cleared an area, install a root barrier (a solid plastic edging at least 200 mm deep) along garden bed edges to prevent kikuyu from creeping back in from adjacent lawn areas. This is a worthwhile long-term investment in any NZ garden where kikuyu is present.
Ongoing Management Tips
| Approach | Best For | Limitations |
|---|---|---|
| Selective herbicide (fluazifop) | Garden beds with broadleaf plants | Won't work on ornamental grasses |
| Glyphosate (spot treatment) | Isolated runners, hard surfaces | Non-selective — use with care |
| Manual removal | Small patches, edible gardens | Time-consuming, must be thorough |
| Solarisation | Large bare areas before replanting | Requires warm weather, 6–8 weeks |
| Root barriers | Preventing re-entry from lawn | Upfront cost and installation effort |
Timing Matters
Kikuyu is most actively growing — and most susceptible to herbicide — during spring and summer. Treatments applied in winter when the grass is semi-dormant are far less effective. Plan your control programme to start in late spring for best results.
When to Call a Professional
If kikuyu has taken over a large area, is intertwined with established plantings, or keeps bouncing back despite your efforts, it's worth calling in a professional landscaper. An experienced landscaper can assess the extent of the infestation, recommend a targeted treatment programme, and help you replant with species that are more competitive against kikuyu regrowth. You can find qualified local landscapers on tradedirectory.co.nz.
Note that herbicide application in some situations (e.g. near waterways) may be subject to regional council rules under the Resource Management Act. Check with your local council before spraying near streams, drains, or wetlands. WorkSafe NZ also provides guidance on safe handling of agrichemicals.
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